Background Noise,
As OS X is a BSD based platform, there is always the super-admin known as root. But direct usage of root is disabled by Apple in normal multi-user mode, you can only access it indirectly via the sudo tool.
But I digress. As far as I know, the user interface of OS X does not permit people to do what you purport to have done... i.e. delete all administrative users only leaving non-administrative users. I believe it forces people to retain at least one user with administrative privileges.
But no matter, you are where you are..... so let's try to fix the mess....
First, let's see if we can do this simply. Do you have an OS X 10.8 DVD ? I'm fairly certain there are menus in there you can use to tweak some stuff, although its been a while since I've booted off a 10.8 disk.
The alternative is longwinded, tedious and involves 100% of your time spent at the command line, which is a scary proposition if you've not spent much time there before....
As for the data ... it depends what you told OS X when you deleted the user. As I recall, it gives you two options "delete user" or "delete user and associated data".
Specifically, we'd like to be able to see a folder in the Finder, Go, Option, library/application support which doesn't appear. We know the data is somewhere as it is available to the associated app.
Actually, just a side-thought.
I trust you are aware that separate users on OS X have separate library etc. level folders (e.g there is a system level /Library and then user level ~/Library).
So it may be as simple as you having to poke around the ~/Libary of the deleted user rather than your user ? (assuming as mentioned earlier, you didn't choose the "delete data" option when trashing the user).
Sniff around the /Users/ directory level and see what you find in terms of your previous account.